The Summer Palace is Wintery

The budgies seem to be greatly enjoying the summer palace, but last night it was down to about 50 degrees Farhenheit and tonight, even down to 45. I hope they do ok! They have been covered with blankets. Interestingly, they have not climbed up to their usual sleeping postures (as high as possible, hanging by their beaks and holding on with their toes on the vertical cage bars below). Tonight, they are sitting in a "traditional" posture, on perches, in the middle portion of the cage, and with heads tucked under wings. Could this be a much warmer way to sleep? I feel rather anxious letting them sleep outdoors in this weather, but am going to allow it. I certainly hope this is the right decision.